In the past, an illumination apparatus provided with a lamp socket for holding a fluorescent lamp has been extensively used as an illumination apparatus for home or various kinds of facilities. As one example of the lamp socket, there is available a waterproof socket endowed with a waterproof property or a dustproof property in consideration of its use in an outdoor area or around water.
As one example of this kind of waterproof socket, there is known a waterproof socket capable of holding a straight tube fluorescent lamp (not shown) as shown in FIG. 12 (see, e.g., Japanese Patent Application Publication No. 2001-52830 (JP2001-52830A)). The waterproof socket includes a socket body 711 having an insertion hole for receiving a pair of lamp pins protruding from an end cap of a straight tube fluorescent lamp, a second waterproof packing 715 and a tightening sleeve assembly 714 detachably attached to the socket body 711 to cover and conceal the outer circumferential surface of the end portion of the straight tube fluorescent lamp. The tightening sleeve assembly 714 includes a tightening sleeve 717, a slip ring 718, a first waterproof packing 713 and a packing presser 719.
In this regard, the socket body 711 includes a base portion 721, a thread coupling portion 722 having a male thread 725 formed on the outer circumferential surface of a portion connected to the base portion 721, a packing rest 723 and a front wall 724 configured to close the front surface of the thread coupling portion 722. On the outer circumferential surface of the thread coupling portion 722, there is provided a proximal portion 722a serving as a packing fitting portion. The second waterproof packing 715 is fitted to the proximal portion 722a. In the thread coupling portion 722, there is provided a lamp pin insertion groove 726 lying at the tip end of the socket body 711 and extending across the male thread 725. In the front wall 724, there is formed a lamp pin rotating groove 727 having a bifurcated shape.
An inwardly-tapered edge portion 731 is formed in the opening of the tightening sleeve 717. A female thread threadedly coupled to the male thread 725 is formed on the rear inner circumferential surface of the tightening sleeve 717. The slip ring 718 is accommodated within the tightening sleeve 717 to make contact with the inner surface of the inwardly-tapered edge portion 731. The first waterproof packing 713 and the packing presser 719 are accommodated within the tightening sleeve 717. The first waterproof packing 713 is interposed between the packing presser 719 and the slip ring 718. The slip ring 718 is used to enable the tightening sleeve 717 to easily rotate with respect to the first waterproof packing 713 when rotationally operating the tightening sleeve 717 in a tightening direction. The packing presser 719 is fitted to the inner circumferential surface of the first waterproof packing 713. An outwardly-facing flange 741 making contact with the first waterproof packing 713 is formed in the packing presser 719. A plurality of engaging lugs 742 protrudes backward from the flange 741. As the engaging lugs 742 come into engagement with engaging recesses 728, the packing presser 719 is restrained from circumferentially rotating with respect to the socket body 711.
As another example of this kind of waterproof socket, there is known a waterproof socket 75 capable of holding a straight tube fluorescent lamp 77 as shown in FIGS. 13 and 14 (see, e.g., JP2001-52830A).
The waterproof socket 75 includes a socket body 711 for receiving lamp pins 77b protruding from an end cap 77a of a straight tube fluorescent lamp 77. The waterproof socket 75 further includes a second waterproof packing 715 and a tightening sleeve assembly 714 detachably attached to the socket body 711 to cover the end portion of the straight tube fluorescent lamp 77.
In this regard, the tightening sleeve assembly 714 includes a tightening sleeve 717, a first waterproof packing 713 and a packing presser 719. The socket body 711 includes a base portion 721, a thread coupling portion 722 having a male thread 725 formed on the outer circumferential surface of a portion connected to the base portion 721, a packing rest 723 and a front wall 724 configured to close the front surface of the thread coupling portion 722. On the outer circumferential surface of the thread coupling portion 722, there is provided a proximal portion 722a serving as a packing fitting portion. The second waterproof packing 715 is fitted to the proximal portion 722a. In the thread coupling portion 722, there is provided a lamp pin insertion groove 726 lying at the tip end of the socket body 711 and extending across the male thread 725. In the front wall 724, there are provided an entrance 727a formed continuously with the lamp pin insertion groove 726 and a lamp pin rotating groove 727 having a bifurcated shape. Attachment grooves 721a for engaging with a socket mount not shown in the drawings are formed on the opposite side surfaces of the base portion 721.
An inwardly-tapered edge portion 731 is formed in the opening of the tightening sleeve 717. A female thread 732 threadedly coupled to the male thread 725 is formed on the rear inner circumferential surface of the tightening sleeve 717. The first waterproof packing 713 and the packing presser 719 are accommodated within the tightening sleeve 717. The first waterproof packing 713 is interposed between the packing presser 719 and the tightening sleeve 717. A plurality of engaging lugs 742 protrudes backward from the packing presser 719. The engaging lugs 742 engage with engaging recesses 728 of the socket body 711. The packing presser 719 includes an inwardly-tapered packing pressing flange 719a formed at the front end thereof. Drive-in lugs 719b protrude from the front surface of the packing pressing flange 719a. In addition to the engaging lugs 742, a plurality of hooking lugs 719c is formed in the rear end portion of the packing pressing flange 719a to protrude outward. The hooking lugs 719c are elastically deformed to climb over a portion of the female thread 732 and to come into a thread groove.
As the waterproof socket 75 is assembled together, the first waterproof packing 713 is deformed to make close contact with the outer circumferential surface of the straight tube fluorescent lamp 77. This makes it possible to assure waterproof.
In recent years, an LED lamp using light emitting diodes becomes widespread. The LED lamp is longer in lifespan than a fluorescent lamp and is capable of reducing power consumption. There are also developed a straight tube LED lamp as an alternative light source of the straight tube fluorescent lamp and an illumination apparatus for a straight tube LED lamp. The straight tube LED lamp includes two lamp pins protruding from one end cap of a tube body and one lamp pin protruding from the other end cap of the tube body. Japanese Lamp Industries Association enacts a standard (JEL801:2010) entitled “Straight Tube LED Lamp System (for General Light Purpose) Provided with L-Type-Pin End Cap GX16t-5”.
Just like the conventional straight tube fluorescent lamp, the straight tube LED lamp requires a waterproof socket endowed with a waterproof property or a dustproof property in consideration of its use in an outdoor area or around water.
The straight tube LED lamp includes an earth end cap provided with one earth lamp pin and a power-feeding end cap provided with two power-feeding lamp pins. The earth end cap needs to be electrically connected to the earth prior to connecting the power-feeding end cap to a power source. This necessitates a waterproof socket of rotary structure to which a straight tube LED lamp can be mounted by rotating the LED lamp about the center axis thereof. In case of the waterproof socket for a straight tube fluorescent lamp, it is sometimes required to use a waterproof socket of rotary structure in order to prevent a human from touching the other lamp pin while one lamp pin is electrically connected to the waterproof socket and supplied with electric power.
The waterproof socket disclosed in JP2001-52830A is a socket of plug-in structure to which a straight tube fluorescent lamp is mounted by inserting the lamp pins of the lamp into insertion holes. If no change is made, the waterproof socket cannot be used in mounting a straight tube LED lamp. It is thinkable that the waterproof socket disclosed in JP2001-52830A is applied to the rotary socket. However, if the waterproof socket disclosed in JP2001-52830A is merely applied to the rotary socket, there may be sometimes generated co-rotation by which the straight tube LED lamp is unintentionally rotated together with the tightening sleeve 717 when tightening the tightening sleeve 717 to the socket body 711. In particular, the straight tube lamp is easy to rotate about the center axis thereof in the rotary waterproof socket to which the straight tube lamp such as a straight tube LED lamp or a straight tube fluorescent lamp is mounted by rotating the lamp about the center axis thereof.
In the waterproof socket applied to the rotary socket, it is therefore likely that the electric connection between the straight tube lamp and the waterproof socket becomes poor.
In case of the straight tube LED lamp, the light irradiated by the LED lamp has directivity. If the LED lamp is not mounted to the socket in a specified position due to the co-rotation of the LED lamp, there is posed a problem in that the inaccurate mounting of the LED lamp tends to affect the distribution of the light irradiated from the LED lamp.
In the straight tube LED lamp provided with an L-type end cap complying with the standard stated above, it is sometimes the case that, unlike the straight tube fluorescent lamp, the outer diameter of the end cap is larger than the outer diameter of the light emitting tube.
In the event that the waterproof socket 75 disclosed in JP2001-52830A is applied to a waterproof socket for holding a straight tube LED lamp, the light emitting tube needs to be brought into close contact with the first waterproof packing 713 after the end cap is inserted into the tightening sleeve assembly 714. This is because the outer diameter of the end cap is larger than the diameter of the light emitting tube. In the waterproof socket 75 for the straight tube LED lamp, the first waterproof packing 713 needs to be deformed more largely than in the waterproof socket 75 for the straight tube fluorescent lamp 77 so that the first waterproof packing 713 can be brought into close contact with the light emitting tube smaller in outer diameter than the end cap. If the deformation amount of the first waterproof packing 713 is too large, unintentional buckling is generated before the first waterproof packing 713 makes contact with the light emitting tube of the straight tube LED lamp. Therefore, there is a possibility that the first waterproof packing 713 gets away from the opening of the tightening sleeve 717 to the outside of the waterproof socket 75. In this case, a problem is posed in that the adhesion between the waterproof socket 75 and the straight tube LED lamp becomes insufficient and the moisture is easily infiltrated into the waterproof socket 75.